A power conversion device applied to an uninterruptible power supply device and the like generally includes a converter for converting alternating current (AC) power from a commercial AC power supply into direct current (DC) power, and an inverter for converting the DC power into AC power having desired frequency and voltage.
For example, WO 2010/095241 (PTL 1) discloses an uninterruptible power supply device constituted of a power conversion device including three-level converters and three-level inverters. In the power conversion device, each of the three-level converters and the three-level inverters includes a plurality of semiconductor switching elements.
In the power conversion device described above, an overcurrent or an overvoltage may occur when any of the plurality of semiconductor switching elements is damaged and is short-circuited. In PTL 1, a fuse is connected between one terminal of each semiconductor switching element and a DC bus (a DC positive bus, a DC negative bus, or DC neutral point bus). With such a configuration, when any of the plurality of semiconductor switching elements is short-circuited, a fuse is blown and a path through which a current flows is cut off, and thereby occurrence of an overcurrent or an overvoltage can be prevented.